Actually, with Crassus... wasn't it like he fell in battle, they cut off his head and presented it to the King during a play (where bacchants tear apart some hero and a head is brought in)? Gold might have come afterwards. But the gold thingy happened to a Roman proconsul for sure, it was Persians too. Also, Mithridates built up an immunity to EVERYTHING and it hilariously backfired.